Nontarnishing detergent composition



United States Patent 2,992,996 NONTARNISHING DETERGENT COMPOSITION Jay C. Harris, Dayton, Ohio, assignor to Monsanto Chemical Company, St. Louis, Mo., a corporation of Delaware No Drawing. Filed Nov. 21, '1956, Ser. No. 623,536

'10 Claims. (Cl. 252-452) The present invention relates to novel detergent compositions and methods of washing metallic objects containing copper such as cutlery in order to avoid tarnishing cutlery.

It is known that, certain metals and alloys, especially those containing copper such as German silver or brass, or plated objects containing such alloys become objectionablydisoolored, tarnished or corroded when contacted with solutions containing synthetic detergents.

It is an object of this invention to provide improved detergent compositions containing an inhibitor which is effective to prevent such discoloration.

According to the present invention there are provided detergent compositions containing organic nitrogen compounds having the formula:

CHz-CH,

CHr-N N-X Hz-N where X is an alkyl radical having from 4 to 24 carbon atoms and preferably from 14 to 22 carbon atoms.

Examples of compounds having the above formula are: 1 butylamino 2,3,5,6 tetrahydro 1 imidaz(1,2-a)- imidazole, 1-pentylamino-2,3,5,6-tetrahydro-1-imidaz(1,2- a) -irnidazole, 1-nhexylamino-2,3,5,6-tetrahydro-l-imidaz- (1,2-a) imidazole, 1 heptylamino-2,3,5,6-tetrahydro-limidaz(1,2-a)-imidazole, 1-n-octylamino-2,3,5,6-tetrahydro-1-imidaz( 1,2-a) -irnidazole, l,2-ethylhexylamino-2,3,5, 6-tetrahydro-1-imidaz(1,2-a)-imidazole, as representative of lower members of the series or 1-dodecylamino-2,3,5,6- tetrahydro-1-imidaz( 1,2-a) -imi= dazole, 1-tetradecylamino- 2,3,5 ,6 tetrahydro 1 imidaz(1,2-a)-imidazole, l-hexadecylamino- 2,3,5,6 tetrahydro 1 imidaz(l,2-a) -imidazole, l-octadecylamino-2,3,5,6-tetrahydro-1-imidaz(1,2- a) imidazole, l-tetracosylamino-2,3,5,6-tetrahydro-1-imidaz( 1,2-a) -imidazole as representative of'higher members of the series. 7 s H r The above imidazole compounds are prepared by contacting the alkylamine, which it is desired to have present in the final compound with 1-( ,B-hydroxyethy-D-Z-methylmercapto-2 -imidazoline toform an intermediate which is chlorinated and then dehydrochlorinated to give the desired 1-alky1amino-2,3,5,6-tetrahydro-l-imidaz(1,2-a)-imidazole. The method ofpreparation is described in copending application Serial No. 574,588, now US. Patent No. 2,782,205.

The above imidazole compounds are well defined stable compounds which range from viscous liquids to waxy or crystalline solids. They are particularly valuable as componentsof detergent compositions in order to reduce the tarnishing of copper-containing alloys when cutlery articles of such alloys are washed with synthetic detergents.

It is an object of the invention to provide detergent compositions which may be employed in washing soiled cutlery and dishes which remain in contactwith the detergent solution for prolonged periods of time. It has been found that cutlery articles, including knives, forks, spoons and other tableware made of German silver and similar copper base alloys, are normally discolored by solutions containing high concentrations of conventional, organic, non-ionic or anionic detergent compouds. This is commonly observed in the washing of soiled cutlery and other household utensils consisting of copper base alloys, particularly during air drying, under which conditions residual amounts of detergent solutions may remain in contact with the cutlery for prolonged periods of time. For example, forks and spoons exhibit tarnishing at those contact points from which the residual solution is evaporated at the conclusion of the washing operation. Plated cutlery made from a base of a copper alloy also exhibits this tarnishing if the plating is scratched or thin, and such tarnishing action may extend over the entire piece of cutlery.

It has now been found that the tarnishing or discoloration effect upon copper alloys, which is characteristic of non-ionic and anionic synthetic detergent compounds and detergents containing the same may be inhibited by the combination therewith of a l-alkylam-ino-2,3,5,6-tetrahydro-l-imidaz(l,2-a)-imidazole in minor proportions suflicient to inhibit the said tarnishing. The alkyl radical in the above compound has from 4 to 24 carbon atoms, and preferably from 14 to 22 carbon atoms. A preferred proportion of the imidazole employed to reduce discoloration and tarnishing in a detergent composition is from 0.01% to 0.5 by weight based upon the synthetic organic detergent. The mechanism of the inhibitory effect is not known, but it has been found that relatively small proportions of these compounds are effective in overcoming the tarnishing effect of the chemical compounds utilized in detergent compositions. The small proportions of the imidazole compounds described above are without effect on the detergency of the mixture.

The synthetic organic anionic and non-ionic detergent components employed in the present invention include the sulfate and sulfonate type compounds as typical anionic detergents. Representative compounds of the non-ionic type are the ethers and esters (including sulfur-containing derivatives and analogues) of polyalkylene glycols and polyglycerols. Mixtures of the above detergent components may also be employed.

The aliphatic sulfated or sulfonated detergents which are employed in combination with the imidazole may have from 8 to 26 carbon atoms. Such detergents include the aliphatic substituted acyl-containing compounds having an alkyl radical of about 9 to 18 carbon atoms such as the aliphatic carboxylic ester detergents. Examples of aliphatic anionic detergents are the sulfuric acid esters of polydric alcohols incompletelyesterified with higher fatty acids, for example, cocoanut oil mono-glyceride monosulfate, tallow diglyceride mono-sulfate, the long-chain pure or mixed higher, primary and secondary alkyl sulfates, such as lauryl sulfate, cetyl sulfate, and higher fatty acid alcohol sulfates derived from reduced cocoanut oil fatty acids. Other detergent compounds which may be used in combination with the 1-alkylamino-2,3,5,6-tetrahydro-1-imidaz(l,2-a) -imidazole include the hydroxy sulfonated higher fatty esters, for example, the higher fatty acid esters of 2,3-dihydroxy propane sulfonic acid, and

the higher fatty esters of low molecular weight alkylol sulfonic acids, such as the oleic ester of isethionic acid. The invention also contemplates the use of higher fatty ethanol-amide sulfates, the higher fatty acid amides of amino alkyl sulfonie acids, for example, lauric amide of taurine, etc. Fhe salts of the various compounds em- Patented July 18, 1961 ployed in the present invention are preferably the sodium, ammonium or potassium salts.

One of the preferred types of detergent components is is a sodium or ammonium sulfonate of an alkyl-substituted aromatic hydrocarbon selected from the group consisting of benzene, toluene and xylene, wherein the alkyl group has from 9 to 18 carbon atoms. The said alkylaryl hydrocarbon is sulfon'ated and is then neutralized with a, sodium, potassium or ammonium alkaline cont; pound to obtain the corresponding sodiumfpotassiuin, alkanolammonium, or ammonium salt. In the preparaation of the alkylaryl sulfonate, the alkyl group is preferably of about 9 to 18 carbon atoms average length, such as may be obtained from olefins or from kerosene. The kerosene may be chlorinated and the aromatic compound alkylated therewith in known manner. Compounds of the sulfonate type are described in [5.5. Patents 2,232,117 and 2,232,118 to Kyrides. A preferred compound of this type is sodium dodecyl benzene sulfonate, also known as sodium tetrapropyl benzene sulfonate when derived from tetrapropylene and benzene.

Other compounds of the above category of anionic detergents having utility in the present invention include the sulfated esters such as the sulfated esters of succinic acid and of sulfophthalic acid. Examples of such compounds which may be employed in the present detergent compositions are the sodium salt of dioctyl sulfosuccinate, sodium hexyl-4-sulfophthalate and octadecyl sulfophthalate. The present invention may also employ sulfonates of an acid which is esterified with a monohydric alcohol. A salt of this type ofcompound is sodium tridecyl f3- sulfopropionate.

Another group of useful detergent compounds are the sulfated and sulfonated anionic detergentsbased on alkyl phenols of long chain, fatty alcohols and tall oil condensed with ethylene oxide or propylene oxide. Examples of such compounds are the sodiunnammoniunr or amine (erg, triethanolamine) salts of nonyl phenol condensed with ten moles of ethylene oxide and then sulfated, while another useful compound is tridecanol which has been condensed with ten moles of ethylene oxide and then sulfated.

The anionic detergents are generally employed in the form of water-soluble salts, such as the alkali metal salts described above. However, the alkaline earth metal, ammonium, amine, and alkylolamine salts are likewise of utility in the present invention. While the sodium, potassium, ammonium and alkylolamine (e.g., mono-, diand triethanolamine) salts are ordinarily preferred, other salts such as the lithium and magnesium salts may be used if desired. For certain purposes, for example, Where it is desired to attain the maximum solubility, the ammonium and alkylolamine salts are preferred.

condensate type is the product obtained by the condenation ftall oi w t ylene xide. Thecondensation of tall oil with ethylene oxide may be conducted with from 1 to 20 moles of ethylene oxide per mole of the tall oil, a preferred range being from 5 to 15 moles of ethylene oxide. Another condensation product of this type which is useful in the present invention is the product resulting from the condensation of tertiary octyl or nonyl phenol with from 5 to 20 moles of ethylene oxide per mole of the said phenol.

Polyoxyethylenecompounds containing sulfur are. also of utility. A compound of this type which may be em ployed in the present invention is the condensation product of a tertiary mercaptan having from 6 to 20 carbon atoms, condensed with from 5 to 20 moles of ethylene oxide per mole of mercaptan.

The above-described polyalkylene condensation. products may be prepared from propylene oxide as well as with ethylene oxide. Admixtures of these two condensing agents may also be employed.

Another synthetic, organic detergent component which maybe employed in the present invention is a compound selected from the group of alkanolami-des of fatty acids,

preferably having from 10 to 20 carbon atoms. A preferred compound of this type is lauric diethanolamide.

ployed for this purpose. For example, an alkanolamide may be prepared from the fatty acids derived from tall oil during the purification and fractionation thereof. The alkanolamine which is employed to form the preferred, alkylolamides may be monoor diethanolamine, mono or diisopropanolamine, or monoor di-n-propanolamine. Preferred amines are diethanolamine and mono-ethanolamine.

Other sources of fatty acids which may be used in the preparation of the alkylolamides are the naturally occur-ring fatty acids, such as those derived from cocoanut oil. presentpreferred group of fatty acidshaving from 1 0 to 20 carbon atoms in the acid radical.

In addition to the above-described synthetic, organic detergent components, the present compositions may in elude builders such as inorganic phosphate and. sulfate salts. The preferred amounts of builders arev from 99 to 20 parts by weight of the inorganic builders, the balance of the solids to make 100 parts consisting of the synthetic, organic detergent.

The P ent invention onte a he o mu a isn, of detergent compositions including a variety of polys rh tss preferred compounds. being le t dfwm the group consisting of tripolyphosphates, pyrophosphates,

hexametaphosphates, tetraphosphates, and mixtures there- The non-ionic compounds which are employedin the configuration of an alcohol produced by the 0x0 proc-,,

ess from an olefin such as triisobutylene or tetrapropylene, with from 1 to 20 moles of ethylene oxideper mole of alcohol. A preferred range is from 5 to 10 moles of, ethylene oxide. The present invention includes. the usev of a mixture of isomeric monohydric primary tridecyl.

alcohols, said alcohols being derived from the oxapme ess carried out with a material of. the class consisting; of. polybutylenes and polypropylenesl Another detergent, component :of. the polyoxyethylene of. 'Ihesodium and ammonium salts are ordinarily em ployed, but the potassium salts may similarly be employed, particularly in the formulation of liquid detergent concentrates. Other. inorganic salts such as the sodiunr silicates mayalso be utilized in -the compositions of the;

inthe scope of the invention.

The present invention also includes liquid formulations which may contain from 30% to 75 7q,iand pref; erablyfrom 40% to 65% by weight of water basedupon the total liquid detergent. Alcohols such; as ethanohand glycols such as ethylene glycol may also be presenttoimprove solubility of the various components. The proportion of alcohol or glycol may be from 1% to- 20% by weight of the. mixture.

The following examples illustrate. specific embodiments {of the. invention. i 7

stant, s fp n wnsis naofa plut stt ee l h i ns dien' swas rep red ep r be ee h t ewe shts of sies ewysc mmune.

The said cocoanut oil fatty acids are within the table also sets forth the preferred range of proportions of the respective components:

A similar mixture using the above detergent composi tion without an inhibitor was prepared as a control, while a third detergent mixture used benzotriazole in the same proportion as a tarnish inhibitor.

The above detergent compositions were dissolved in water at 0.20 weight percent concentration, and tested as described below in order to determine the relative effectiveness of the contained tarnish inhibitor. The tests were conducted upon small samples of German silver which had first been polished with croscus cloth, and then washed and rinsed in acetone. The metal test samples were exposed in a half submerged position in a beaker containing the respective detergent composition solution.

The exposure was continued for a period of 24 hours at a temperature of approximately 70 F. At the conclusion of this time the metal samples were removed and examined to determine the extent of the discoloration. The rating system used was based on a visual examination as to whether the degree of discoloration was severe or slight, employing the following scale of values.

--None 1Very slight corrosion at air-solution interface only 2-Slight, at air-solution interface only 3-Considerable 4-Severe A number of additional related compounds were included in the tests. The test data are summarized below:

Discoloration inhibitor: Discoloration rating 1 butylamino-2,3,5,6 tetrahydro 1 imidaz- (1,2-a) imidazole 2 1-tetradecy1amino-2,3,5,6 tetrahydro 1 imidaz- (1,2-a) imidazole 1 1-hexadecylamino-2,3,5,6-tetrahydro 1 imidaz- (1,2-a) imidazole 1 The above data indicate that the combination of a 1- alkylamino 2,3,5,6 tetrahydro 1 imidaz(1,2-a)- imidazole, together with a synthetic, organic detergent component resists the tarnishing effect which is otherwise characteristic of the detergent composition employed alone.

The detergent compositions of the present invention are of particular utility in dishwashing. It is, accordingly, an embodiment of the present invention to wash cutlery in an aqueous washing solution. The preferred concentration of the present detergent composition containing the above imidazole derivative is from 0.05% to 0.5% by Weight of the detergent product in the said dishwashing solution. The essential ingredient is the combination of a synthetic, organic detergent compound of the anionic or non-ionic type, together with a minor tarnishing of copper base alloys by the said detergent compound.

What is claimed is:

1. A detergent composition comprising a synthetic, organic detergent selected from the group consisting of anionic and non-ionic detergents which normally tarnish copper base allows, and in combination therewith a small amount of a 1-alkylamino-2,3,5,G-tetrahydro 1 imidaz- (1,2-a)-imidazole in which the alkyl radical has from 4 to 24 carbon atoms sufl'lcient to inhibit tarnishing of the copper base alloy.

2. A detergent composition comprising a synthetic, organic detergent selected from the group consisting of anionic and non-ionic detergents which normally tarnish copper base alloys, and in combination therewith a small amount of 1-octadecy1arnino-2,3,5,6-tetrahydro-1-imidaz- (1,2-a)-imidazole sufficient to inhibit tarnishing of the copper base alloy.

3. A detergent composition comprising a synthetic, organic detergent selected from the group consisting of anionic and non-ionic detergents which normally tarnish copper base alloys, and in combination therewith a small amount of 1-butylamino-2,3,5,6,-tetrahydro 1 imidaz- (1,2-a)-imidazole sufiicient to inhibit tarnishing of the copper base alloy.

4. A detergent composition comprising a synthetic, organic detergent selected from the group consisting of anionic and non-ionic detergents which normally tarnish copper base alloys, and in combination therewith a small amount of tetradecylamino-2,4,5,6-tetrahydro-1- imidaz(1,2-a) imidazole sufiicient to inhibit tarnishing of the copper base alloy.

5. A detergent composition comprising a synthetic, organic detergent selected from the group consisting of anionic and non-ionic detergents which normally tarnish copper base alloys, and in combination therewith a small amount of 1-hexadecylamino-2,3,5,6-tetrahydro-1-imidaz- (1,2-a)-imidazole sufficient to inhibit tarnishing of the copper base alloy.

6. The method of washing cutlery made of a copper base alloy which comprises subjecting said cutlery to an aqueous solution of a detergent composition comprising a synthetic, organic detergent selected from the group consisting of the anionic and non-ionic detergents which normally tarnish said cutlery, and in combination therewith about 0.01% to 0.5 by weight based upon said detergent of a 1-alkylamino-2,3,5,6'tetrahydro-1-imidaz(1,2-a)- imidazole in which the alkyl radical has from 4 to 24 carbon atoms to inhibit tarnishing of said cutlery.

7. The method of washing cutlery made of a copper base alloy which comprises subjecting said cutlery to an aqueous solution of a detergent combination comprising a synthetic, organic detergent selected from the group consisting of the anionic and non-ionic detergents, which normally tarnish said cutlery, and in combination therewith about 0.01% to 0.5% by weight based upon said detergent of 1-octadecyla.mino-2,3,S,6-tetrahydroimidaz(1, 2-a)-irnidazole, to inhibit tarnishing of the said cutlery.

8. The method of washing cutlery made of a copper base alloy which comprises subjecting said cutlery to an aqueous solution of a detergent composition comprising a .synthetic, organic detergent selected from the group consisting of the anionic and non-ionic detergents, which normally tarnish said cutlery, and in combination therewith about 0.01% to 0.5 by weight based upon said detergent of 1-butylarnino-2,3,5,6-tetrahydro-1-imidaz(1,2- a)-imidazole, to inhibit tarnishing of the said cutlery.

9. The method of washing cutlery made of a copper base alloy which comprises subjecting said cutlery to an aqueous solution of a detergent composition comprising a synthetic, organic detergent selected from the group consisting of the anionic and non-ionic detergents, which normally tarnish said cutlery, and in combination therewith about 0.01% to 0.5% by weight based upon said deter- 7 gentv of tetradecylamino-2,3,5,6'tetrahydro-1-imidaz(1,2- a)-imidazole, to inhibit tarnishing of the said cutlery.

10. The method of Washing cutlery made of a copper base alloy which comprises subjecting said cutlery to an aqueous solution of a detergent composition comprising a synthetic, organic detergent selected from the group consisting of the anionic and non-ionic detergents, which normally tarnish said cutlery, and in combination therewith about 0.01% to 0.5% by Weight based upon said deter- 8 gent of 1-hexadecylamino-2,3,5,6-tetrahydro-1-imidaz(1,2- a)-imidazole, to inhibit tarnishing of the said cutlery.

References Cited in the file of this patent UNITED STATES PATENTS 2,618,605 Schaeffer Nov. 18, 1952 2,618,608 Schaeifer Nov. 18, 1952 2,733,215 Ruff Jan. 31, 1956 2,782,205 McKay Feb. 19, 1957 

1. A DETERGENT COMPOSITION COMPRISING A SYNTHETIC, ORGANIC DETERGENT SELECTED FROM THE GROUP CONSISTING OF ANIONIC AND NON-IONIC DETERGENTS WHICH NORMALLY TARNISH COPPER BASE ALLOWS, AND IN COMBINATION THEREWITH A SMALL AMOUNT OF A 1-ALKYLAMINO-2,3,5,6-TETRAHYDRO - 1 - IMIDAZ(1,2-A)-IMIDAZOLE IN WHICH THE ALKYL RADICAL HAS FROM 4 TO 24 CARBON ATOMS SUFFICIENT TO INHIBIT TARNISHING OF THE COPPER BASE ALLOY. 